A key component in semiconductor application is a solid-state switch. As an example, switches turn loads of automotive applications or industrial applications on and off. Solid-state switches typically include, for example, field effect transistors (FETs) like metal-oxide-semiconductor FETs (MOSFETs) or insulated gate bipolar transistors (IGBTs).
In order to realize self-protecting power switches, it is customary inter alia to integrate a current sensor. The current sensor may be realized as a small sensor transistor, which supplies a current proportional to the load current flowing through the load transistor. The sensor transistor is substantially smaller, e.g. a factor of 1000-50000 smaller than the load transistor, and a sensor current flowing through the sensor transistor is smaller than the load current through load transistor ideally by the geometrical ratio of the active areas of the two transistors, namely the load transistor and the sensor transistor.
The actual ratio of the current flowing through the load transistor and the current flowing through the sensor transistor may depend on process variations and on operating conditions like the operating temperature. This is because of partially commonly used conduction paths between sense and load transistor and partially separate conduction paths. It is thus desirable to provide a semiconductor device, in which the dependence of the actual ratio of the load transistor and sensor transistor currents on process variations and operating conditions is reduced.